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            <div><h5 class="title">
                <a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2"></a><a class="link"
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                                                                                                    title="basic_datagram_socket::native_non_blocking (2 of 3 overloads)">basic_datagram_socket::native_non_blocking
                (2 of 3 overloads)</a>
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    <p>
        <span class="emphasis"><em>Inherited from basic_socket.</em></span>
    </p>
    <p>
        Sets the non-blocking mode of the native socket implementation.
    </p>
    <pre class="programlisting"><span class="keyword">void</span> <span
            class="identifier">native_non_blocking</span><span class="special">(</span>
    <span class="keyword">bool</span> <span class="identifier">mode</span><span class="special">);</span>
</pre>
    <p>
        This function is used to modify the non-blocking mode of the underlying
        native socket. It has no effect on the behaviour of the socket object's
        synchronous operations.
    </p>
    <h6>
        <a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2.h0"></a>
        <span><a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2.parameters"></a></span><a
            class="link"
            href="overload2.html#asio.reference.basic_datagram_socket.native_non_blocking.overload2.parameters">Parameters</a>
    </h6>
    <div class="variablelist">
        <p class="title"><b></b></p>
        <dl>
            <dt><span class="term">mode</span></dt>
            <dd><p>
                If <code class="computeroutput"><span class="keyword">true</span></code>, the underlying
                socket is put into non-blocking mode and direct system calls may
                fail with <code class="computeroutput"><span class="identifier">asio</span><span
                    class="special">::</span><span class="identifier">error</span><span class="special">::</span><span
                    class="identifier">would_block</span></code>
                (or the equivalent system error).
            </p></dd>
        </dl>
    </div>
    <h6>
        <a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2.h1"></a>
        <span><a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2.exceptions"></a></span><a
            class="link"
            href="overload2.html#asio.reference.basic_datagram_socket.native_non_blocking.overload2.exceptions">Exceptions</a>
    </h6>
    <div class="variablelist">
        <p class="title"><b></b></p>
        <dl>
            <dt><span class="term">asio::system_error</span></dt>
            <dd><p>
                Thrown on failure. If the <code class="computeroutput"><span class="identifier">mode</span></code>
                is <code class="computeroutput"><span class="keyword">false</span></code>, but the
                current value of <code class="computeroutput"><span class="identifier">non_blocking</span><span
                    class="special">()</span></code> is <code class="computeroutput"><span
                    class="keyword">true</span></code>,
                this function fails with <code class="computeroutput"><span class="identifier">asio</span><span
                    class="special">::</span><span class="identifier">error</span><span class="special">::</span><span
                    class="identifier">invalid_argument</span></code>,
                as the combination does not make sense.
            </p></dd>
        </dl>
    </div>
    <h6>
        <a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2.h2"></a>
        <span><a name="asio.reference.basic_datagram_socket.native_non_blocking.overload2.example"></a></span><a
            class="link"
            href="overload2.html#asio.reference.basic_datagram_socket.native_non_blocking.overload2.example">Example</a>
    </h6>
    <p>
        This function is intended to allow the encapsulation of arbitrary non-blocking
        system calls as asynchronous operations, in a way that is transparent
        to the user of the socket object. The following example illustrates how
        Linux's <code class="computeroutput"><span class="identifier">sendfile</span></code> system
        call might be encapsulated:
    </p>
    <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span
            class="keyword">typename</span> <span class="identifier">Handler</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">sendfile_op</span>
<span class="special">{</span>
  <span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span
                class="special">&amp;</span> <span class="identifier">sock_</span><span class="special">;</span>
  <span class="keyword">int</span> <span class="identifier">fd_</span><span class="special">;</span>
  <span class="identifier">Handler</span> <span class="identifier">handler_</span><span class="special">;</span>
  <span class="identifier">off_t</span> <span class="identifier">offset_</span><span class="special">;</span>
  <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span
                class="identifier">total_bytes_transferred_</span><span class="special">;</span>

  <span class="comment">// Function call operator meeting WriteHandler requirements.</span>
  <span class="comment">// Used as the handler for the async_write_some operation.</span>
  <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span
                class="identifier">asio</span><span class="special">::</span><span class="identifier">error_code</span> <span
                class="identifier">ec</span><span class="special">,</span> <span class="identifier">std</span><span
                class="special">::</span><span class="identifier">size_t</span><span class="special">)</span>
  <span class="special">{</span>
    <span class="comment">// Put the underlying socket into non-blocking mode.</span>
    <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span
                class="special">)</span>
      <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">sock_</span><span
                class="special">.</span><span class="identifier">native_non_blocking</span><span
                class="special">())</span>
        <span class="identifier">sock_</span><span class="special">.</span><span
                class="identifier">native_non_blocking</span><span class="special">(</span><span
                class="keyword">true</span><span class="special">,</span> <span class="identifier">ec</span><span
                class="special">);</span>

    <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">ec</span><span
                class="special">)</span>
    <span class="special">{</span>
      <span class="keyword">for</span> <span class="special">(;;)</span>
      <span class="special">{</span>
        <span class="comment">// Try the system call.</span>
        <span class="identifier">errno</span> <span class="special">=</span> <span class="number">0</span><span
                class="special">;</span>
        <span class="keyword">int</span> <span class="identifier">n</span> <span class="special">=</span> <span
                class="special">::</span><span class="identifier">sendfile</span><span class="special">(</span><span
                class="identifier">sock_</span><span class="special">.</span><span
                class="identifier">native_handle</span><span class="special">(),</span> <span
                class="identifier">fd_</span><span class="special">,</span> <span class="special">&amp;</span><span
                class="identifier">offset_</span><span class="special">,</span> <span class="number">65536</span><span
                class="special">);</span>
        <span class="identifier">ec</span> <span class="special">=</span> <span class="identifier">asio</span><span
                class="special">::</span><span class="identifier">error_code</span><span class="special">(</span><span
                class="identifier">n</span> <span class="special">&lt;</span> <span class="number">0</span> <span
                class="special">?</span> <span class="identifier">errno</span> <span class="special">:</span> <span
                class="number">0</span><span class="special">,</span>
            <span class="identifier">asio</span><span class="special">::</span><span
                class="identifier">error</span><span class="special">::</span><span class="identifier">get_system_category</span><span
                class="special">());</span>
        <span class="identifier">total_bytes_transferred_</span> <span class="special">+=</span> <span
                class="identifier">ec</span> <span class="special">?</span> <span class="number">0</span> <span
                class="special">:</span> <span class="identifier">n</span><span class="special">;</span>

        <span class="comment">// Retry operation immediately if interrupted by signal.</span>
        <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span> <span
                class="special">==</span> <span class="identifier">asio</span><span class="special">::</span><span
                class="identifier">error</span><span class="special">::</span><span
                class="identifier">interrupted</span><span class="special">)</span>
          <span class="keyword">continue</span><span class="special">;</span>

        <span class="comment">// Check if we need to run the operation again.</span>
        <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span> <span
                class="special">==</span> <span class="identifier">asio</span><span class="special">::</span><span
                class="identifier">error</span><span class="special">::</span><span
                class="identifier">would_block</span>
            <span class="special">||</span> <span class="identifier">ec</span> <span class="special">==</span> <span
                class="identifier">asio</span><span class="special">::</span><span class="identifier">error</span><span
                class="special">::</span><span class="identifier">try_again</span><span class="special">)</span>
        <span class="special">{</span>
          <span class="comment">// We have to wait for the socket to become ready again.</span>
          <span class="identifier">sock_</span><span class="special">.</span><span
                class="identifier">async_wait</span><span class="special">(</span><span
                class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span
                class="special">::</span><span class="identifier">wait_write</span><span class="special">,</span> <span
                class="special">*</span><span class="keyword">this</span><span class="special">);</span>
          <span class="keyword">return</span><span class="special">;</span>
        <span class="special">}</span>

        <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ec</span> <span
                class="special">||</span> <span class="identifier">n</span> <span class="special">==</span> <span
                class="number">0</span><span class="special">)</span>
        <span class="special">{</span>
          <span class="comment">// An error occurred, or we have reached the end of the file.</span>
          <span class="comment">// Either way we must exit the loop so we can call the handler.</span>
          <span class="keyword">break</span><span class="special">;</span>
        <span class="special">}</span>

        <span class="comment">// Loop around to try calling sendfile again.</span>
      <span class="special">}</span>
    <span class="special">}</span>

    <span class="comment">// Pass result back to user's handler.</span>
    <span class="identifier">handler_</span><span class="special">(</span><span class="identifier">ec</span><span
                class="special">,</span> <span class="identifier">total_bytes_transferred_</span><span class="special">);</span>
  <span class="special">}</span>
<span class="special">};</span>

<span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span
                class="identifier">Handler</span><span class="special">&gt;</span>
<span class="keyword">void</span> <span class="identifier">async_sendfile</span><span class="special">(</span><span
                class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span><span
                class="special">&amp;</span> <span class="identifier">sock</span><span class="special">,</span> <span
                class="keyword">int</span> <span class="identifier">fd</span><span class="special">,</span> <span
                class="identifier">Handler</span> <span class="identifier">h</span><span class="special">)</span>
<span class="special">{</span>
  <span class="identifier">sendfile_op</span><span class="special">&lt;</span><span
                class="identifier">Handler</span><span class="special">&gt;</span> <span
                class="identifier">op</span> <span class="special">=</span> <span class="special">{</span> <span
                class="identifier">sock</span><span class="special">,</span> <span class="identifier">fd</span><span
                class="special">,</span> <span class="identifier">h</span><span class="special">,</span> <span
                class="number">0</span><span class="special">,</span> <span class="number">0</span> <span
                class="special">};</span>
  <span class="identifier">sock</span><span class="special">.</span><span class="identifier">async_wait</span><span
                class="special">(</span><span class="identifier">tcp</span><span class="special">::</span><span
                class="identifier">socket</span><span class="special">::</span><span
                class="identifier">wait_write</span><span class="special">,</span> <span
                class="identifier">op</span><span class="special">);</span>
<span class="special">}</span>
</pre>
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